Do joint-preserving hip procedures compromise subsequent total hip arthroplasty? A meta-analysis of complications, functional outcome and survivorship

Background: Joint-preserving hip operations can help relieve pain and delay the need for long-term joint arthroplasty. Previous research has not identified procedures that can compromise outcomes following total hip arthroplasty (THA). This meta-analysis aims to evaluate the effect of joint-preserving hip operations on outcomes following subsequent THA. Methods: MEDLINE, EMBASE and Scopus databases were searched from the date of inception until February 2024. All studies comparing outcomes following THA in individuals with (PS) and without prior surgery (NPS) of the femur or pelvis were included. Data on operative time, blood loss, intra- and post-operative complications, functional outcomes, and implant survivorship were extracted. Results: 16 studies, comprising 2576 patients were included (PS = 939, NPS = 1637). The PS group was associated with significantly longer operative time [MD: 8.1, 95% CI: 4.6–11.6], significantly greater blood loss [MD: 167.8, 95% CI: 135.6–200.0], and a higher risk of intra-operative peri-prosthetic fracture [RR: 1.9, 95% CI: 1.2–3.0], specifically, with prior femoral osteotomy. There were no differences in terms of risks of dislocation [RR: 1.8, 95% CI: 1.0–3.2], implant loosening [RR: 1.0, 95% CI: 0.7–1.5], or revision surgery [RR: 1.3, 95% CI: 1.0–1.7] between the two groups. The PS group was associated with significantly poorer improvements in functional outcome [MD: −5.6, 95% CI: −7.6–(−3.5)], specifically, with prior acetabular osteotomy. Implant survivorship in the two groups was comparable after one year [HR: 1.9, 95% CI: 0.6–6.2] but significantly inferior in the PS group after five years [HR: 2.5, 95% CI: 1.4–4.7], specifically, with prior femoral osteotomy. Conclusion: Joint-preserving hip operations are associated with greater intra-operative challenges and complications. In subsequent joint arthroplasty, prior acetabular procedures affect functional outcomes while prior femoral procedures influence implant survivorship. Hip pain due to the morphological sequelae of pediatric hip pathology can be debilitating at a young age. Surgical decision-making at that time needs to consider the survivorship of a THA implanted at that young age against the consequences of hip preservation surgery on further THA.


Introduction
Joint-preserving hip procedures encompass a variety of operations including arthroscopy, acetabular and femoral osteotomies, fibular grafts, and fusion [1,2].The principles of treatment are to relieve pain and improve function, thus, delaying the need for long-term total hip arthroplasty (THA) [1,3,4].These procedures are used in managing the sequelae of childhood disorders such as developmental dysplasia of the hip (DDH), Perthes disease, and slipped capital femoral epiphysis (SCFE) [1].
THA in patients with prior acetabular and femoral osteotomies can be more technically challenging.However, data on clinical and functional outcomes following THA in this population has yielded mixed results, which can be attributed to poor study quality, bias and confounding influences, and the absence of long-term follow-up [3].It is generally acknowledged that femoral osteotomies involving realignment of the proximal femoral canal make arthroplasty more challenging, but it is unclear whether complications are significantly increased in hip arthroplasty as a result of prior femoral or acetabular surgery.
There is a clear clinical need to understand how prior acetabular or femoral osteotomies can influence outcomes following THA in this patient population.The present metaanalysis aims to evaluate the effect of joint-preserving hip procedures on outcomes following subsequent THA.

Material and methods
Literature search methods, inclusion and exclusion criteria, outcome measures and statistical analysis were defined according to the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) [5].Patients were not involved in the conception, design, analysis, drafting, interpretation or revision of this research.Thus, ethics approval was not required.

Search strategy
The following databases were searched, the last search on 14th February 2024: (a) MEDLINE (1946 until May 2023) via OvidSP; (b) MEDLINE in-process and other non-indexed citations (latest issue) via OvidSP; (c) Ovid EMBASE (1974 to latest issue); (d) Scopus (1996 till present).Three search strings were used, which were then linked by the AND modifier.First search string: "pelvis" OR "hip" OR "femur" OR "acetabulum"; second search string: "total hip arthroplasty" OR "total hip replacement"; third search string: "osteotomy" OR "graft" OR "rod" OR "fusion" OR "arthrodesis".Truncated search terms utilizing the wildcard character and the "related articles" function were used to broaden the search.Additionally, the references of included articles were hand-searched to identify any additional studies.

Study selection
All observational studies that compared outcomes following THA in individuals with and without prior surgery of the femur or pelvis were included.The following inclusion criteria were applied: (a) adult population with or without a history of surgery to the femur or pelvis in childhood; (b) THA in adulthood; and (c) compared outcomes following THA.However, studies that included individuals in whom the index surgery was due to trauma were excluded.The following additional exclusion criteria were applied: (a) non-English language; (b) non-human studies; (c) experimental trials; (d) review articles; (e) editorials; (f) case reports; (g) case series; (h) letters; (i) conference abstracts; and (j) unpublished studies.

Outcome measures
The following outcome measures were evaluated: (a) operative time; (b) blood loss; (c) intra-and post-operative complications for which we pragmatically accepted the definitions provided by the authors; (d) implant survivorship as defined by the time from surgery to revision; (e) radiological outcome as defined by component positioning, wear or loosening; and (f) functional outcome as defined by validated outcome scores (e.g.Harris Hip Score, Oxford Hip Score).Studies that reported at least one of the outcomes of interest were included in the meta-analysis.The primary outcome was implant survivorship as this was considered to be the most reliable and consistent measurement.

Data extraction
Two independent reviewers (E.L.G and O.R.B.) screened all the titles and abstracts for inclusion, both of whom were blinded to authors, journals, institutional affiliations and dates of publication.Both reviewers evaluated each selected reference independently and summarized relevant study characteristics.In case of disagreement, a consensual decision between the two reviewers under the involvement of a third independent reviewer (T.D.) was reached.The following data items were extracted: the year of publication, study design, sample size, type of patients, patient characteristics and outcome measures.

Quality and risk of bias assessment
The Methodological Index for Non-Randomized Studies (MINORS) was used for quality and risk of bias assessment [6].The risk of publication bias was assessed using a funnel plot.Assessments of publication bias for each study design were performed separately.The quality of evidence was assessed as per GRADE.Quality assessment was carried out by two independent reviewers.

Statistical analysis
Risk ratio (RR), mean difference (MD) and hazard ratio (HR) are presented with 95% confidence intervals (CI).HR was used as a summary statistic for long-term outcomes (survival analysis) as described by Parmar et al. [7].Review Manager 5.4 (Cochrane Collaboration, Oxford, United Kingdom) was used for data analysis.Medians were converted to means using the formula described by Hozo et al. [8].The fixed-effects model was used to pool the results.The standard heterogeneity test, the I 2 statistic, was used to assess the consistency of the effect sizes, which indicates the percentage of the variability in effect estimates because of true between-study variance rather than within-study variance.Statistical heterogeneity was defined as low, moderate and high with an I 2 of above 25%, 50% and 75%, respectively [9].Results above 60% were considered as substantial heterogeneity.Subgroup analyses based on the type of prior surgery (e.g.femoral osteotomy, pelvic osteotomy) performed were conducted.

Study characteristics
A total of 16

Quality assessment and risk of bias
A maximum score of 24 points was used for all comparative studies.The median MINORS score was 18 points, with a range of 15-21 points.Overall, the studies included scored well in terms of the presence of a clearly stated aim, use of endpoints appropriate to the study, use of an unbiased assessment of the study endpoints, an adequate control group, and adequate statistical analyses (Table 3).However, the studies included scored poorly in terms of performing a prospective calculation of the study size, inclusion of consecutive patients, and prospective collection of data.Publication bias was assessed with the use of a funnel plot and presented for the outcome, revision surgery (Figure 2).The overall risk of publication bias was deemed to be low.

Intra-operative outcomes
Intra-operative outcomes including operating time, blood loss, peri-prosthetic fracture, and nerve injury were reported in 13 studies, comprising 2018 patients (Figure 3).Eight studies with 767 patients reported data on operating time, which was significantly longer in the PS group by an MD of 8.12 [95% CI: 4.61, 11.62, p < 0.00001, I 2 = 92%] (Figure 3a).Subgroup analyses demonstrated that this significant difference was attributed to prior femoral osteotomy.There was significant heterogeneity in the data and the evidence was deemed to be of low quality.
Blood loss was reported by eight studies of 767 patients (Figure 3b).There was significantly greater blood loss in the PS group, with an MD of 167.87 [95% CI: 135.59, 199.97, p < 0.00001, I 2 = 92%].Subgroup analyses revealed that this significant difference was due to prior femoral osteotomy.Significant heterogeneity was present in the data and the evidence was deemed to be of low quality.The incidence of peri-prosthetic fracture was reported by seven studies with 1498 patients, which was significantly higher in the PS group, with an RR of 1.85 [95% CI: 1.16, 2.98, p = 0.01, I 2 = 50%] (Figure 3c).Subgroup analyses demonstrated that this significant difference was attributed to prior femoral osteotomy.There was moderate heterogeneity in the data and the evidence was deemed to be of moderate quality.
Seven studies comprising 1488 patients reported whether nerve injury was present (Figure 3d).There was no significant difference between the PS and NPS groups, with an RR of 1.85 [95% CI: 0.84, 1.14, p = 0.13, I 2 = 0%].Subgroup analyses did not identify any procedures that were associated with an increased risk of nerve injury.No heterogeneity was present in the data and the evidence was deemed to be of moderate quality.

Post-operative clinical outcomes
Post-operative clinical outcomes including surgical site infection (SSI), dislocation, peri-prosthetic fracture, aseptic loosening, revision surgery, and venous thromboembolism (VTE) were reported by 13 studies comprising 2429 patients (Figure 4).The incidence of SSI was reported by nine studies of 1557 patients, and was significantly higher in the PS group by an RR of 3.37 [95% CI: 1.53, 7.46, p = 0.003, I 2 = 0%] (Figure 4a).Subgroup analyses did not identify differences in risk of SSI between different procedures.There was no heterogeneity in the data and the evidence was deemed to be of moderate quality.
The risk of dislocation was reported in 11 studies comprising 1815 patients (Figure 4b).There was no significant difference between the PS and NPS groups, with an RR of 1.77 [95% CI: 0.98, 3.18, p = 0.06, I 2 = 0%].Subgroup analyses did not identify any procedures that were associated with an increased risk of dislocation.No heterogeneity was present in the data and the evidence was deemed to be of moderate quality.
Four studies with 1006 patients reported the occurrence of peri-prosthetic fracture (Figure 4c).No significant difference was observed between the two groups, with an RR of 4.15 [95% CI: 0.72, 23.81, p = 0.11, I 2 = 0%].Subgroup analyses did not identify differences in the risk of peri-prosthetic fracture between different procedures.There was no heterogeneity in the data and the evidence was deemed to be of low quality.
The incidence of aseptic loosening was reported in 10 studies comprising 1339 patients, which showed comparable risk between the PS and NPS groups, with an RR of 1.00 [95% CI: 0.68, 1.47, p = 1.00,I 2 = 0%] (Figure 4d).Subgroup analyses did not identify any procedures that were associated with an increased risk of aseptic loosening.No heterogeneity was present in the data and the evidence was deemed to be of moderate quality.
Overall, 12 studies with 2296 patients reported the risk of revision surgery (Figure 4e).There was no significant difference between the two groups, with an RR of 1.27 [95% CI: 0.97, 1.66, p = 0.09, I 2 = 0%].Subgroup analyses did not identify any procedures that were associated with an increased risk of revision surgery.There was no heterogeneity in the data and the evidence was deemed to be of low quality.
Five studies with 636 patients documented the occurrence of venous thromboembolism (VTE) (Figure 4f).No significant difference was observed between the two groups, with a RR of 0.72 [95% CI: 0.22, 2.33, p = 0.58, I 2 = 0%].Subgroup analyses demonstrated comparable risk across all procedures and the evidence was deemed to be of low quality.

Implant survivorship
Data regarding implant survivorship was available from five studies of 885 patients, with at least five years of follow-up (Figure 5).At one-year, implant survivorship between the PS and NPS groups was comparable with an HR of 1.90 [95% CI: 0.58, 6.18, p = 0.29, I 2 = 39%].At five years, the PS group had significantly inferior implant survivorship with an HR of 2.54 [95% CI: 1.37, 4.71, p = 0.003, I 2 = 37%].Subgroup analyses observed this difference to be due to prior femoral osteotomy.Low heterogeneity was present in the data and the evidence was deemed to be of moderate quality.

Functional outcome
Seven studies, comprising 1209 patients, provided functional outcome scores in the form of the Harris Hip Score (HHS) (Figure 6).Compared to the NPS group, the PS group experienced a significantly poorer improvement in HHS with an MD of À5.58 [95% CI: À7.64, À3.52, p < 0.00001, I 2 = 40%].Subgroup analyses identified that this was attributed to prior acetabular osteotomy.Low heterogeneity was present in the data and the evidence was deemed to be of moderate quality.

Discussion
The present meta-analysis reports intra-operative, postoperative clinical and functional outcomes, and implant In this study, THA in patients with prior femoral osteotomy was associated with significantly longer operating time, greater blood loss, and elevated risk of peri-prosthetic fracture.Femoral osteotomy leads to distortion of the proximal femur, thus, making subsequent THA more technically challenging [14].In particular, preparation of the femoral canal for the implant is affected by displacement of the femoral shaft, angulation of the femur or retained hardware [18].Duncan et al. reported longer operating time and greater blood loss in the prior femoral osteotomy cohort, which corroborate our current findings [3].
Inferior clinical outcomes were initially observed in these patients undergoing prior joint-preserving hip procedures, although these studies lacked robustness and methodological rigour due to the lack of control and comparator groups [26,27].Subsequent systematic reviews reporting comparable clinical outcomes have challenged these observations [3,4].The risk of SSI is markedly increased in patients with any prior joint-preserving hip procedure, which is in line with previous data [14].However, the risks of dislocation, peri-prosthetic fracture, aseptic loosening, and revision surgery do appear comparable.Implant survivorship of THA following prior femoral osteotomy was significantly poorer at five years follow-up, which contrasts with previous work by Duncan et al. [3] and Gallazi et al. [4].Nonetheless, evaluation of the data suggests that the difference in implant survivorship can be attributed to the higher risk of prosthetic joint infection (PJI) following THA in patients with prior femoral osteotomy.Prior reviews have also been limited by the inclusion of studies with small cohorts, significant heterogeneity and lack of imputable survivorship data, all of which increase the probability of a Type II error.
The functional improvement conferred by THA appears to be compromised by prior acetabular osteotomy.Acetabular osteotomy alters the anatomy and version of the acetabulum.Hence, retroversion of the acetabular component of the implant may occur, which could explain the smaller functional improvement following THA [28].Our updated analysis includes new studies with larger cohorts, thus, addressing the inadequate power, common to prior reviews evaluating THA following prior acetabular osteotomy [3].This is the first study to report this and highlights the need for further analysis of hip centre and version alteration at the time of the hip preservation surgery.As with femoral osteotomies, there is more than one type of acetabular procedure and these need further evaluation.
This meta-analysis highlights the technical challenges of THA in patients with prior femoral osteotomy; notably, the increased operating time, blood loss and risk of peri-prosthetic fracture, as well as poorer long-term implant survivorship.However, consideration must be given to the type of femoral osteotomy performed when using this information for clinical decision-making.It is unlikely that just the act of femoral osteotomy is responsible but more probably the type and location.The complications are related to additional procedures required to normalise hip morphology to accommodate an implant in THA.Thus, while osteotomies in a subtrochanteric location will deform the femur and increase problems, it is possible that this is not true of trochanteric osteotomies and intra-articular osteotomies.Further studies are required to examine this.
There are several limitations that should be taken into consideration in the present meta-analysis.The studies included are retrospective in nature and therefore, susceptible to inherent biases and confounding influences [29].Additionally, survivorship data is reported inconsistently by different studies, so a degree of imputation is required in our analysis.There was insufficient information to perform subgroup analyses to evaluate how much of the true effect size could be attributed to the choice of implant as well.

Conclusion
This analysis shows that caution should be exercised when considering femoral osteotomies in patients who may later require THA as there is an association with reduced implant survivorship and peri-prosthetic fracture.Surgical decisionmaking for these complex cases is best managed by a highvolume hip preservation surgeon in conjunction with an arthroplasty surgeon specializing in complex primary and revision surgery, whilst ensuring the patient and their family are fully informed.

Figure 1 .
Figure 1.Study flowchart showing screening and selection process.

Figure 2 .
Figure 2. Funnel plot assessing publication bias for the outcome, revision surgery.

Figure 3 .
Figure 3. Intra-operative outcomes of total hip arthroplasty with and without prior bone surgery.(a) Operating time, (b) blood loss, (c) periprosthetic fracture and (d) nerve injury.

Figure 5 .
Figure 5. Implant survivorship with and without prior bone surgery.(a) One-year follow-up and (b) five years follow-up.

Table 3 .
MINORS quality and risk of bias assessment.